This invention relates to single lens reflex cameras.
A typical prior art single lens reflex camera is illustrated in FIG. 1. The camera has a focal plane shutter of the laterally operating type. That is, the shutter includes two blades that are movable relative to each other so as to define an exposure slit that extends parallel to axes defined by film supply and take up spools. A patrone chamber 5 surrounds the film supply spool. Film (not shown) is drawn from the supply spool so as to extend along the rear side of a mirror box 6. A drive sprocket 2 provides for advancing the film to the take-up spool 1. A take-in drum 3 and a spring drum 4 are provided for directly controlling the mechanical operation of the shutter blades in a well known manner.
It is characteristic of cameras of this type of construction that the drums 3 and 4 are positioned on opposite sides of the mirror box 6. To provide such a camera with electric circuit elements forming part of a built-in automatic exposure control system, several approaches can be taken. Among these approaches are:
A. The circuit elements are divided so as to be adapted for a limited space and mounted;
B. The camera body is partially enlarged when the space is too small to accommodate the elements even in the divided accommodation as mentioned above in (a); and
C. The camera body is enlarged to provide a space sufficiently large for mounting of the circuit elements.
Each of these methods has disadvantages as well as advantages.
The method mentioned in (a) is advantageous in that the camera need not be unduly bulky, but is disadvantageous in that division of the circuit elements necessarily complicates the wiring and, as a result, not only the accuracy of mounting work becomes poor but also the reliability is reduced since failures often occur due to such poor accuracy of mounting work. Furthermore, this method is further disadvantageous in that it is difficult to check and adjust the circuit system as a whole and many steps for these purposes are necessary in connection with after-sale servicing of such circuitry.
The methods mentioned in (b) and (c) each at least to some extent reduce the disadvantages of the method (a), However, the method (b) inevitably leads to the disadvantage that the camera body must be bulky and, in practice, cannot perfectly eliminate the disadvantages of the method (a).
The method mentioned in (c) is advantageous as to facilitating mounting work in assembly and as to the reliability of performance. These advantages arise because the camera body may be enlarged to conform with required configuration of the wiring plates or circuit boards. Another advantage thereof is that operations such as checking and adjustment of circuit units and maintenance in after-sale service are facilitated. Nevertheless, this method too suffers from the disadvantage that the camera body must be bulky.
In summary of the foregoing, obtaining advantages such as the facility of assembly work, the desired realiability and the convenience for after-sale service is counterbalanced by the disadvantage of a bulky camera body. If the desired circuit elements are incorporated into a compact camera body, none of the advantages as above mentioned could be obtained.